The infection of mammalian and insect cells with SFV bearing nsP1 palmitoylation mutations.

Semliki Forest virus (SFV), an alphavirus, replicates in vertebrate host and mosquito vector cells. The virus-specific part of the replicase complex constitutes nonstructural proteins 1-4 (nsP1-nsP4) and is bound to cytoplasmic membranes by an amphipathic helix inside of nsP1 and through the palmitoylation of cysteine residues in nsP1. In mammalian cells, defects in these viral functions result in a nonviable phenotype or the emergence of second-site compensatory mutations that have a positive impact on SFV infection.